In LTE (Long Term Evolution) and LTE-Advanced designed by 3GPP (3rd Generation Partnership Project) which is a project aiming to standardize a mobile communication system, an “X2 interface”, which is a network interface established between base stations, is defined (for example, refer to Non-patent Document 1).
The X2 interface is used for inter-base station communication in a handover procedure of a user terminal and CoMP (Coordinated Multipoint Transmission) in which a plurality of base stations communicate with a user terminal in cooperation with each other.